83Plus:OS:84 Plus USB Information

OK, I've started this talk page to post information about the 84 Plus USB. This isn't the ideal place, since not all of this stuff has to do with entry point 5254, but it'll have to do. If anyone else would like to contribute any information or thoughts, please do so. Much of this data has been discovered by analyzing how the EasyData application interacts with the EasyTemp probe. --Dan Englender 22:32, 23 May 2005 (PDT)

The USB entry points that Easy Data uses are:

5254
5257
525A
525D
5260

These routines return carry flag with an error code in A on failure, or no carry on success. The entry points seem to be called only on initialization and quit. On initialization 5254 then 525D are called, and then 525A six times. On quit, 5254, then 5260, then 5257 are called.

The 5254 entry point seems to take a callback address to be passed in A (page) and HL (address). That callback address appears to be called on quit, after 5257 is called.

The 5260 and 5257 entry points are called right after each other in the code, and don't seem to take any input. I guess they're some kind of USB shut down. 5260 doesn't do much of anything other than set 9C1E to 0000. 5257 plays with the ports some, and then clears the callback address. Since the call back address gets called, I'm assuming it must also call the callback address somewhere in there.

525A and 525D take some kind of input in HL. I'm not sure what yet.

The callback routine appears to recieve some kind of input in B. I'm not sure what yet.